EP1196346B1 - Method for filling a container - Google Patents

Abstract

A method of filling a receptacle with a net weight substance by means of a filler member disposed to introduce the substance into the receptacle while the receptacle is being carried by a force sensor, the method comprising at least one cycle comprising the steps of:placing the receptacle on the force sensor;commanding the filler member to start a flow of the substance;repeatedly measuring the time for which the substance has been flowing since the start-of-flow command was issued;measuring a value of a signal supplied by the force sensor at least at first and second separate measurement instants;calculating a mean flow rate of the substance over the time interval between the measurement instants;making at least one computed evaluation of a filling time on the basis of the calculated mean flow rate and a reference weight; andcommanding the flow of substance to stop when the flow time of the substance is equal to the evaluated filling time.

Description

The present invention relates to a method of filling a container with a net weight of product at means of a filling member arranged to introduce the produced in the container while it is carried by a force sensor.

We know different filling processes of a container with a net weight of product. Traditionally, the simplest method is to have a container on a weighing member, the container itself being arranged below a filling member whose opening and closure are controlled by the weighing device according to the apparent weight that is measured by it. The weight apparent not only includes the empty weight of the container and the net weight of the product contained in the container, but also the force that results from the jet of product on the surface of the product contained in the container. This strength varies not only according to the opening of the organ filling but also depending on the viscosity of the product, so that if the viscosity of the product varies during filling, the measurement of weight made by the weighing device is distorted and the actual net weight of product introduced into the container at the end of filling does not equal the net weight of desired product.

In addition, at the time of the closure of the filling, the product between the filling member and the product surface in the container, usually called drop tail, just increase the weight product finally contained in the container at the end of filling cycle. The weight of the fall tail varies in function of the diameter of the orifice of the filling member just before closing and the viscosity of the product. In traditional processes, jet pressure during the filling and the weight of the drop tail must therefore be compensated for eventually getting into the container the net weight of desired product.

We also know French patent 2,679,516 a filling process of slaving the flow of the produced on a reference flow and to perform the filling for a predetermined fixed time calculated in advance by dividing the net weight by the reference flow. This process eliminates the effects of jet pressure on the surface of the product contained in the container in measuring instantaneous flow over time intervals successive times during which the force of the product jet on the surface of the product contained in the container is assumed constant. This process is theoretically very satisfying but in practice the enslavement of the flow on a flow of reference does not allow to obtain a real flow exactly equal to the reference flow and it is therefore necessary to compensate by carrying out a control of the actual net weight after filling and by changing the servo loop parameters for the cycles of subsequent filling so that the actual net weight is also as close as possible to the desired net weight.

We still know French document 2,711,610 a filling process comprising the steps of measuring over successive time intervals the instantaneous flow of product introduced into the container, calculate a weight total product introduced into the container from instantaneous flow over each time interval, and order a stop of the product flow when the total calculated weight reaches the net weight decreased by the tail of product drop. This method has the advantage of automatically take into account flow variations snapshot when calculating the total product weight in a container so the actual net product weight contained in the container after the closure of the organ of filling is only theoretically affected by the variations of the fall tail whose influence is weak. However, when introducing the container onto the organ of weighing and the establishment of the product stream during the flow control, the weighing member is subject to oscillations that distort the measurement of instantaneous flow and consequently the calculation of the total weight of product contained in the container. To overcome this drawback is necessary to filter the signal of the weighing member, at least in the initial phase of filling, by complex algorithms that significantly increase the cost of implementation of this filling process.

An object of the present invention is to propose a method of filling a container that can be put into work with simple algorithms while allowing to obtain a great precision on the net weight of product introduced into the container.

• disposer un récipient sur le capteur de force,
• commander un écoulement de produit par l'organe de remplissage,
• décompter de façon répétée un temps d'écoulement de produit depuis la commande d'écoulement,
• mesurer à au moins un premier et un deuxième instants de relevé séparés une valeur d'un signal fourni par le capteur de force,
• calculer un débit moyen de produit dans un intervalle de temps séparant les instants de relevé,
• effectuer au moins une évaluation calculée d'un temps de remplissage à partir du débit moyen calculé et d'un poids de référence,
• commander un arrêt de l'écoulement de produit lorsque le temps d'écoulement de produit est égal à l'évaluation du temps de remplissage.

With a view to achieving this object, the invention proposes a method of filling a container with a product by means of a filling member arranged to introduce the product into the container while it is being carried. by a force sensor, this method comprising at least one cycle comprising the steps of:

• have a container on the force sensor,
• controlling a flow of product through the filling member,
• repeatedly counting a product flow time from the flow control,
• measuring at least a first and a second separate measurement times a value of a signal supplied by the force sensor,
• calculate an average product flow in a time interval separating the recording times,
• perform at least one calculated evaluation of a filling time from the calculated average flow rate and a reference weight,
• controlling a stop of the product flow when the product flow time is equal to the evaluation of the filling time.

Thus, the step of calculating an average flow of product minimizes the consequences of initial oscillations so that a precise result is achieved without it being necessary to use complex calculation algorithms.

According to an advantageous version of the invention, a smoothed average flow rate is calculated by choosing moments of staggered readings relative to the flow control of sufficient way for the force sensor to be substantially stable over the time interval between moments of survey. The period of instability from cycle is thus automatically eliminated.

• disposer un récipient d'initialisation sur le capteur de force,
• de préférence, mesurer un poids à vide de référence du récipient au moyen du capteur de force et mémoriser le poids à vide de référence,
• commander un écoulement de produit par l'organe de remplissage,
• décompter de façon répétée un temps d'écoulement de produit depuis la commande d'écoulement,
• calculer au moins une fois le débit moyen lissé de produit,
• effectuer au moins une évaluation calculée d'un temps de remplissage à partir du débit moyen lissé et d'un poids net de produit souhaité,
• commander un arrêt de l'écoulement de produit lorsque le temps d'écoulement de produit est égal à l'évaluation du temps de remplissage,
• mesurer le poids du récipient après remplissage et en déduire une différence entre le poids net de produit souhaité et un poids net réel de produit dans le récipient,
• calculer le poids de référence en déduisant du poids net souhaité la différence entre le poids net souhaité et le poids net réel.

According to a preferred embodiment of the invention, the method comprises an initialization cycle comprising the steps of:

• have an initialization container on the force sensor,
• preferably, measuring a reference empty weight of the container by means of the force sensor and storing the reference empty weight,
• controlling a flow of product through the filling member,
• repeatedly counting a product flow time from the flow control,
• calculate at least once the smoothed product flow rate,
• perform at least one calculated evaluation of a filling time from the smoothed average flow rate and a desired net product weight,
• controlling a stop of the product flow when the product flow time is equal to the evaluation of the filling time,
• measuring the weight of the container after filling and deducting a difference between the net weight of desired product and a net actual product weight in the container,
• calculate the reference weight by deducting from the desired net weight the difference between the desired net weight and the actual net weight.

Thus, the initialization cycle implements substantially identical to those of the cycles set works later for the filling of others containers, so that the reference weight is determined without additional cost.

• la figure 1 est un diagramme illustrant l'évolution de la force mesurée par le capteur de force en fonction du temps pendant un cycle de remplissage,
• la figure 2 est une représentation schématique par blocs des étapes de remplissage pendant un cycle d'initialisation selon le mode de mise en oeuvre préféré de l'invention,
• la figure 3 est une représentation schématique par blocs des étapes de remplissage pendant un cycle de remplissage normal selon un mode de mise en oeuvre préféré de l'invention.

Other features and advantages of the invention will appear on reading the following description of a preferred embodiment of the method according to the invention with reference to the attached figs, among which:

• FIG. 1 is a diagram illustrating the evolution of the force measured by the force sensor as a function of time during a filling cycle,
• FIG. 2 is a schematic block representation of the filling steps during an initialization cycle according to the preferred embodiment of the invention,
• Figure 3 is a schematic block diagram of the filling steps during a normal fill cycle according to a preferred embodiment of the invention.

With reference to FIG. 2, the method according to the invention is implemented by a device comprising in a manner known per se a feed member 1 connected to a filling member 2 disposed above a container 3 itself carried by a force sensor 4. The feeding member is for example a tank carried by the platform rotation of a carousel or a separate tank of the carousel and connected to the platform by a pipe with a Turning joint. Flow from the organ feeding can be favored by a centrifugal pump. The filling member 2 is for example a valve or a Archimedes screw controlled by a stepper motor, the speed of the motor determining the flow caused by the screw d'Archimède, particularly in the case of a pasty product such as mayonnaise or a heterogeneous product such only a sauce with pieces. We will notice in this regard that the control of the filling member can not be performed directly on a debit value but on a physical parameter (opening section or speed of rotation of the screw), the actual flow not only dependent the physical parameter ordered but other parameters such that the density of the product, its viscosity and the pressure in the supply duct.

The device also comprises an organ time count 5 including a clock to give a common time base for the different bodies providing the implementation of the method according to the invention.

The diagram in Figure 1 illustrates the evolution of the force measured by the force sensor as a function of time while filling a one-liter bottle with milk. The time of a filling cycle is the order of 5 seconds, which implies an average throughput of the order of 200 grams per second. We imagine easily that such a high flow implies a jet force important. The establishment of the product jet therefore causes a shock on the bottom of the container, which explains the oscillations of the force measured by the force sensor for a little over a second from start of a cycle. It will be noted that these oscillations could be avoided if you expect a stabilization of the sensor force after the introduction of the container and if one performed flow control by increasing throughput in a very gradual way to avoid a shock on the force sensor. Such a solution would, however, an extension of the duration of a filling cycle of totally incompatible with the rates of filling required at present.

According to the preferred embodiment of the invention provides a filling method comprising first an initialization cycle to acquire a number of parameters specific to the installation. During the initialization cycle, a container 3 is disposed on the force sensor 4 and a measurement of the empty weight of the container is carried out after allowing the force sensor to stabilize. The measuring the empty weight of the container used for the cycle initialization is stored and will be subsequently denoted by reference empty weight. A command of the flow is then triggered as well as a count of time to repeatedly measure a time flow of product from the flow control, the counting of time is for example performed at each thousandth of a second. In parallel, a measurement of the signal of strength provided by the force sensor is made to separate recording times, for example every 1 / 250th second. The force signal values thus recorded are used to calculate an average product flow in the time interval separating the times of the survey.

According to the preferred embodiment of the invention, the average flow rate is calculated in two ways different: on the one hand a smoothed average flow calculated in choosing staggered reading instants in relation to the flow control enough so that the force sensor is substantially stable over the interval time separating the times of the survey.

With reference to FIG. 1, the smoothed average flow rate will therefore not be calculated during the period of a little more than one second following the flow command but will be calculated repeatedly thereafter, for example between times T1, T2 and T3 which have been illustrated voluntarily very separately in Figure 1 for better understanding. The smoothed average flow rate is calculated by dividing a force difference between two times of reading by the time counted between these two instants. If we denote by F1 the value of the force measured at time t1, F2 the force measured at time t2 ..., we can calculate a first average flow smoothed between instants t1 and t2 according to the formula D1 = (F2 - F1) / (t2 - t1).

At the subsequent time t3, the smoothed average flow rate can be calculated either by taking the force difference between F2 and F3, or the force difference between F1 and F3 and by dividing this difference by the corresponding counted time. In order to obtain a better smoothing, it is also possible to calculate the smoothed average flow rate by averaging the force measured at different times preceding the time of recording and by calculating the difference in force between the value recorded at the last moment and the average calculated on the previous instants, then dividing by the interval of time taken between the last moment of reading and the average of the instants of statement taken into account for the calculation of the average of the deviations of force. Smoothing can also be performed by averaging several smoothed average flows. Anyway, each calculated smoothed average flow is characteristic of an equation line F = D1.t + B where F is representative of a force applied to the force sensor, i.e., not only the weight of the container and the net weight of product contained in the container, but also the force of the product jet, D1 is the smoothed average flow rate, t is the time taken from the flow control, and B is the ordinate at the origin of the line representative of the smoothed average flow rate, that is to say that B is representative of the sum the empty weight T of the container and the force Fj of the product jet. It will be noted that the force Fj is not directly measurable since it would suppose an instantaneous reaction of the force sensor at the time of the establishment of the jet.

Furthermore, a notional average rate Df is calculated by dividing the value of the force signal at a given instant by the time counted from the flow control. The fictitious average rate is representative of a line joining the origin to the corresponding point of the filling curve. Each calculation of the mean average rate corresponds to a different line. In order not to overload the figure, only the straight lines representative of the imaginary mean flow rates at the instant T2 and at the end of the filling have been represented in FIG. 1. The line representative of the imaginary average flow rate has for equation F = Df.t.

When the smoothed mean flow rate and the mean average flow rate are calculated at the same time of reading, the force measured by the force sensor is the same, it is therefore possible to calculate the ordinate at the origin of the straight line representative of the smoothed flow rate. by the intersection of the lines, either Df.t = D1.t + B from where we draw B = (Df - D1) / t.

During the initialization cycle, the reference empty weight Tr of the container is known. It is therefore possible to calculate a reference jet force Fjr by applying the formula Fjr = Br - Tr where Br is the ordinate at the origin of the straight line representative of the average flow smoothed during the initialization cycle.

Simultaneously with the calculation of the jet force of reference, a calculated evaluation of the time of filling from the average flow smoothed by dividing the net weight of product that one wishes to introduce into the container by the averaged smoothed flow calculated. The weather counted since the flow command is periodically compared to the calculated filling time and a stop flow is controlled when the flow time of product is equal to the evaluation of the filling time.

It should be noted that because of the assimilation was made of the filling curve to a straight and in because of the fact that the weight of the drop tail does not have been taken into account to control the flow stop, the actual net weight of the product contained in the container at the end of the initialization cycle can not be equal to desired net weight.

According to one characteristic of the invention perform a weight measurement in the initialization cycle total after filling and a calculation of the actual net weight per subtraction of the reference empty weight Tr previously memorized, the force sensor is then used in the same way a balance. A reference weight Pr is then calculated subtracting from the desired net weight the difference between actual net weight and desired net weight. From the weight reference Pr can also be calculated a time of ref reference filling by dividing the weight of reference by the average flow smoothed during the cycle initializing.

With reference to Figure 3, the parameters of the initialization cycle are used according to the invention for subsequent filling cycles of the containers. For each filling cycle a container is arranged on the force sensor but unlike the cycle initialization a product flow control by the filling member is immediately performed without it is necessary to wait for a stabilization of the force sensor after the introduction of the container. The flow control can even be anticipated compared at the introduction of the container on the force sensor so that despite the response time of the filling member, the jet of product reaches the container just when this one is set up on the force sensor, which allows to increase the rate of filling. Of the same way that during the initialization cycle a calculation of the smoothed average flow rate and mean fictitious average flow is performed from repeatedly at different times of recording, which allows each time to determine the y-intercept of the right representative of the average flow smoothed as in the initialization cycle.

The calculated value of this ordinate at the origin is this time used to make an estimate of the empty weight T of the container being filled using the reference jet force previously stored by applying the formula T = B - Fjr.

The value of the empty weight of the container as well obtained can be used to control net weight as will be indicated below.

A calculated evaluation of filling time is then performed by dividing the last weight of reference calculated by the last calculated average smooth flow.

A stop command of the product flow is performed when the product flow time counted by the time counting member 5 is equal to estimation of the filling time.

According to the preferred embodiment illustrated in Figure 3, a comparison is made after each evaluation of filling time between the time of calculated fill and refill time calculated at the end of the initialization cycle and if the gap exceeds a critical value, for example 5% of the time of reference filling, the flow stop is ordered using reference refill time and an initialization cycle is started again in order to allow an update of the parameters of installation.

If the time of the filling cycle is sufficiently short compared to the desired rate, a control is preferably carried out at the end of each filling cycle. This control consists of measuring the weight of the filled container, to compare the measured weight to a estimated weight equal to the sum of the estimated curb weight and net weight of desired product. When this control reveals between the measured weight and the estimated weight a gap exceeding a critical value, a new initialization cycle is sets off. This control can also be used without replace the calculated evaluation of the filling time by reference refill time when the evaluation filling time deviates abnormally from the time reference filling.

Of course, the invention is not limited to mode of implementation described and is likely to variants without departing from the scope of the invention as defined by the claims.

In particular, although the acquisition of The parameters of the installation have been described by an initialization cycle, we can expect to obtain these parameters either by calculations or by measurements carried out independently of the implementation of the process filling according to the invention. For example, when containers have a constant curb weight of a container to a other, we can remove the step of measuring the empty weight of the container in the initialization cycle as well as the step of estimating the empty weight of the container in the subsequent filling cycles.

When the settings of the installation are very constant or when the precision constraints of the filling is reduced, it is also possible to simplify the process according to the invention by carrying out a calculated evaluation of the filling time from a only calculation of the average flow, for example about four seconds after the flow control.

Moreover, we can see in Figure 1 that because of the steep slope of the filling curve in its substantially rectilinear part and the small offset of the ordinate at the origin, the line representative of the flow fictitious medium is very close to the filling curve real especially at the end of filling. Without leaving the framework of the invention, it is therefore possible to provide estimating filling time by replacing flow medium smoothed by the average fictitious throughput and perform a correction either by measurements made during a cycle initialization, or by calculated corrections.

In the case of a comparison between the time of rated fill and reference refill time, it is possible to update the filling time of reference by replacing the filling time of initial reference by the last reference time of filling evaluated when the difference does not exceed the value critical. We can also provide a second threshold critical for which an alarm is immediately triggered when the gap between the filling time evaluated and the reference refill time exceeds this second threshold.

Claims (7)

1. A method of filling a receptacle with a net weight substance by means of a filler member disposed to introduce the substance into the receptacle while the receptacle is being carried by a force sensor, the method being characterized in that it comprises at least one cycle comprising the steps of:

   placing the receptacle on the force sensor;

   commanding the filler member to start a flow of the substance;

   repeatedly measuring the time for which the substance has been flowing since the start-of-flow command was issued;

   measuring a value of a signal supplied by the force sensor at least at first and second separate measurement instants;

   calculating a mean flow rate of the substance over the time interval between the measurement instants;

   making at least one computed evaluation of a filling time on the basis of the calculated mean flow rate and a reference weight; and

   commanding the flow of substance to stop when the flow time of the substance is equal to the evaluated filling time.
2. A method according to claim 1, characterized in that a smoothed mean flow rate is calculated by selecting measurement instants that are offset from the start-of-flow command sufficiently for the force sensor to be substantially stable over the time interval between the measurement instants.
3. A method according to claim 2, characterized in that it includes an initialization cycle comprising the steps of:

   placing a receptacle on the force sensor;

   commanding the filler member to start the flow of substance;

   repeatedly measuring a substance flow time from the start-of-flow command;

   calculating at least once the smoothed mean flow rate of the substance;

   calculating at least one evaluation of a filling time on the basis of the smoothed mean flow rate and a desired net weight of substance;

   commanding the flow of substance to stop when the product flow time is equal to the evaluated filling time;

   measuring the weight of the receptacle after filling and deducing therefrom a difference between the desired net weight of substance and the real net weight of substance in the receptacle; and

   calculating the reference weight by subtracting the difference between the desired net weight and the real net weight from the desired net weight.
4. A method according to claim 3, characterized in that it includes a prior step of measuring a reference tare weight of the receptacle by means of the force sensor, and storing the reference tare weight.
5. A method according to claim 3, characterized in that during the initialization cycle, it includes the steps of:

   calculating at least once a simplified mean flow rate between the start-of-flow command and a latest measurement instant;

   calculating the difference between the simplified mean flow rate and the smoothed mean flow rate by reference to a reference tare weight of the receptacle; and

   deducing therefrom a reference jet force of the product and storing it;

      and in that, during each subsequent cycle, it includes the steps of:

   calculating at least once the simplified mean flow rate; and

   calculating the difference between the simplified mean flow rate and the smoothed mean flow rate with reference to the reference jet force and estimating an tare weight for the receptacle that is being filled.
6. A method according to claim 5, characterized in that it includes the steps of measuring the weight of the receptacle, comparing the measured weight with an estimated weight equal to the sum of the estimated tare weight plus the desired net weight of substance, and triggering a new initialization cycle whenever the difference between the measured weight and the estimated weight exceeds a critical value.
7. A method according to claim 6, characterized in that during the initialization cycle it includes, after correcting the reference weight, the steps of evaluating a reference filling time and of storing it, and in that during each subsequent cycle, it includes the steps of comparing the evaluated filling time for the receptacle being filled with the reference filling time and of comparing the measured weight and the estimated weight when a difference between the estimated filling time and the reference filling time exceeds a critical value.

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